The present invention relates to a mortise lock for a window, door or similar.
More specifically the invention is intended for a mortise lock with a housing that is provided with an operating mechanism with a pinion that is turnably mounted in the housing and a rack engaging therewith that is movably affixed in the housing, whereby a turning movement of the pinion, by means of a handle or a key, must be converted into a sliding movement of a rack, which in turn ensures the opening and closing of the lock.
Such a mortise lock is generally built into the space between the fixed frame and the movable leaf of the window, the door or similar, whereby the available space is limited so that in such a case the diameter of the pinion must necessarily be small, for example of the order of magnitude of a maximum of 15 millimetres or even less than 10 millimetres, for the transmission of nonetheless relatively large forces.
Such a mortise lock is known in DE 10.2013.105.303 with an operating mechanism with a pinion and a rack engaging therewith, each with two toothings that are separated from one another by a geometric dividing plane that extends perpendicularly to the axial direction of the pinion and which are both constructed as a straight toothing, in other words a toothing whose faces, viewed in the longitudinal direction, extend parallel to one another and are perpendicular to the aforementioned dividing plane. The teeth of both toothings are in line with one another in this case.
Such a mortise lock is known in BE 1.018.951, as well as an embodiment in which the teeth of the two toothings are offset with respect to one another by one toothing being turned by a half pitch of the teeth with respect to the other toothing, such that a smoother transmission is realised, because in this way when driving the pinion twice the number of transitions is realised between the end of the contact between two teeth of the pinion and the rack, and the start of the contact between the next two teeth of the pinion and the rack.
In both cases a disadvantage is that the transition contact zone is generally small and critical and is usually situated at the level of the top of the teeth where there is a real risk of turning over and a juddery transmission, whereby this risk is all the greater as the diameter of the pinion becomes smaller.
An embodiment is also known in DE 10.2013.105.303 whereby the two toothings are constructed as an oblique toothing with teeth whose faces are parallel but which make an angle to the axial direction, whereby the teeth are oriented such that both toothings together form an arrow toothing.
The arrow toothing ensures that the axial forces cancel out one another, but has just as much the same disadvantage: a real risk of turning over when the diameters of the pinion are small.
Such arrow toothing also has the disadvantage that a complex mould is required to manufacture the pinion out of plastic or metal with a conventional injection moulding technique, and to be able to remove the injected pinion from the mould after injection moulding, which results in a high production cost.